title: The effect of matrix stiffness on the differentiation of mesenchymal stem cells in response to TGF-β.
abstract: Bone marrow mesenchymal stem cells (MSCs) are a valuable cell source for tissue engineering and regenerative medicine. Transforming growth factor β (TGF-β) can promote MSC differentiation into either smooth muscle cells (SMCs) or chondrogenic cells. Here we showed that the stiffness of cell adhesion substrates modulated these differential effects. MSCs on soft substrates had less spreading, fewer stress fibers and lower proliferation rate than MSCs on stiff substrates. MSCs on stiff substrates had higher expression of SMC markers α-actin and calponin-1; in contrast, MSCs on soft substrates had a higher expression of chondrogenic marker collagen-II and adipogenic marker lipoprotein lipase (LPL). TGF-β increased SMC marker expression on stiff substrates. However, TGF-β increased chondrogenic marker expression and suppressed adipogenic marker expression on soft substrates, while adipogenic medium and soft substrates induced adipogenic differentiation effectively. Rho GTPase was involved in the expression of all aforementioned lineage markers, but did not account for the differential effects of substrate stiffness. In addition, soft substrates did not significantly affect Rho activity, but inhibited Rho-induced stress fiber formation and α-actin assembly. Further analysis showed that MSCs on soft substrates had weaker cell adhesion, and that the suppression of cell adhesion strength mimicked the effects of soft substrates on the lineage marker expression. These results provide insights of how substrate stiffness differentially regulates stem cell differentiation, and have significant implications for the design of biomaterials with appropriate mechanical property for tissue regeneration.
authors.affiliation: Department of Bioengineering, University of California, Berkeley, B108A Stanley Hall, Berkeley, CA 94720-1762, USA.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Park
authors.forename: Julia S
authors.initials: JS
authors.lastname: Chu
authors.forename: Anchi D
authors.initials: AD
authors.lastname: Tsou
authors.forename: Rokhaya
authors.initials: R
authors.lastname: Diop
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Tang
authors.forename: Aijun
authors.initials: A
authors.lastname: Wang
authors.forename: Song
authors.initials: S
authors.lastname: Li
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D002448:Cell Adhesion; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation; D002478:Cells, Cultured; D024043:Collagen Type II / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D008071:Lipoprotein Lipase / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D024043:Collagen Type II; D008071:Lipoprotein Lipase; D051899:Smad2 Protein; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; D020741:rho GTP-Binding Proteins; D000099166:Polyacrylamides; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human